The present invention relates to a method of manufacturing a thin film magnetic head, e.g., an induction recording-reproducing thin film magnetic head, a hybrid thin film magnetic head composed of an induction recording head and a magnetoresistance reproducing head, which is used for a magnetic disk drive unit, a magnetic tape recorder, etc., and a magnetic recording-reproducing apparatus.
In an ordinary hybrid MR head (a thin film magnetic head) including an induction recording head and a magnetoresistance reproducing head, a write-head section for induction-recording data is piled on a reproducing head section having a magnetoresistance (MR) element. The structure of the thin film magnetic head is shown in FIGS. 4–6. FIG. 4 is a plan view of the thin film magnetic head; FIG. 5 is a sectional view thereof; and FIG. 6 is a schematic view of a disk-side face thereof.
As shown in FIG. 5, the write-head section has an upper magnetic pole 10 and a lower magnetic pole 12, which mutually faced with a minute gap 5. A coil 14, which is made of an electric conductive material, is formed between the magnetic poles 10 and 12. The lower magnetic pole 12 acts as an upper shielding layer of the reproducing head section. As shown in FIG. 6, a lower shielding layer 18 is provided under an MR element 16.
To improve recording density of a recording medium, track density of the recording medium should be increased. Therefore, width of the write-core section should be made as narrow as possible and as precise as possible. After the upper magnetic pole 10 is formed, the write-core width is determined by ion milling or FIB machining. A sectional shape of the write-core width is examined by SMI test or SEM test. Since a wafer is charged with static electricity during the SMI or SEM test, a whole surface of the wafer is covered with an electric conductive film for preventing the charge of static electricity. Therefore, the electric conductive film is removed by ion milling after the examination of the write-core width of the core section.
The ion milling is applied to the whole surface of the wafer so as to remove the electric conductive film for executing the SEM test. In the case of having the write-core width 1 μm or more, variation of the write-core width caused by ion milling is 0.01–0.02 μm, so that variation cause no problems. However, in the thin film magnetic head for the recent magnetic disk drive unit, the write-core width is 0.2 μm or less; the variation of the write-core width badly influences accuracy and function of products, and it cannot be ignored.